The broad, long-term objectives of the research proposal are to gain a better understanding of the skeletal muscle dysfunction seen in chronic heart failure (CHF), with its associated health-related consequences of diminished functional capacity. Using an epi-illuminated microscope in situ leg muscle preparation in the rat, the specific aims of the research proposal ar to measure CHF-induced abnormalities in skeletal muscle microcirculation an reactivity of pre-capillary arterioles and post- capillary venules. Capillarity and fiber-type composition of the same muscle will subsequently be evaluated by histochemistry. The experimental preparation has the unique advantage in that it will allow for measurements of capillary flow and microvessel reactivity at rest, during muscle contractions, and in response to various vasoconstrictors and vasodilators. In this manner, it will be possible to determine both the degree, and specific location of any impairments in skeletal muscle microcirculation seen with CHF. As mild electrical stimulation has been shown to improve microvascular supply and fatigue in chronically ischemic muscle, this same intervention will also be used in one group of CHF rats to assess its potential as a rehabilitative paradign for CHF patients with associated skeletal muscle dysfunction.